A particular text-transmitting device has dominated the paging industry. That is the "Alphamate" distributed by Motorola Company. The Alphamate is a microprocessor-based device that stores pager data and messages in a random access memory. The pager data consists of the initials of pager users and the identification codes required by an associated paging service to communicate with the pagers. In a message-creating mode, an operator can compose a message on a display using a keyboard and can specify a pager for which the message is intended. The message together with the pager identification code is then added to a transmission queue of like messages in memory. In an entirely separate message-transmitting mode, the microprocessor dials a particular paging service through a modem and transmits all message in succession to the paging service. The messages are then immediately cleared from memory (except for the last-transmitted message), and the message-creating mode can be resumed.
There are several significant limitations to the prior device. It is adapted to communicate only with a single paging service. Unfortunately, paging services observe different communication protocols, including different baud rates, parity, word lengths, and maximum message lengths. A separate device would be required to handle communications with each paging service and would require connection to a separate telephone line. Also, the prior device does not allow concurrent message creation and transmission. While the device is in its message-transmitting mode, the operator is unable to compose and enter messages. Also, the transmission function of the prior device has significant limitations. The device essentially transmits the telephone number of the paging service, and after a period of time transmits its messages in succession. That occurs even when a busy signal is encountered, losing messages. Also retransmission of messages received garbled is not possible, except for the last message that has been transmitted and remains stored.